for some \(\xi _{\alpha (n-2)}\) . In the case of Minkowski space, this theorem was proved in [1]}, [2]}.
Here we start by giving an alternative derivation in Minkowski space,
\(\mathfrak {C}_{\alpha (n)}(h) =0 \quad \Longleftrightarrow \quad h_{\alpha (n)}=\partial _{\alpha (2)}\xi _{\alpha (n-2)}~.\) 
